Assuming you have a uniform expansion of gasses upon their ignition from the top most piston position to the bottom, would the force generated on the crankshaft vary at different points in the down cycle? My logic tells me that when you are in the top most part of the cycle, you would have a tiny component of force directed downwards and most of the force being exerted perpendicular to where you want it to be moving, then as you reach the middle of the cycle, the gases are finally pushing the rod directly downwards and hence peak force and then it tapers off again. Is this correct? Also since a turbine engine is... well different in design, does this difference mean they are more efficient? Yes piston engines also have 4 strokes so they lose efficiency in that regard also but let's disregard that for a second.